Internal combustion engines, such as a gasoline engine, produce a variety of waste gases that are expelled from the cylinders through the cylinder head during operation. A method of managing these gases is to route them away from the cylinder head using an exhaust manifold. The exhaust manifold unifies the expelled waste gases from the cylinders through a series of channels known as runners. Multiple runners can combine to form a larger outlet known as a port (e.g., manifold exhaust port). The output from the port can then be directed towards the desired location such as a turbocharger turbine, exhaust gas recirculation (EGR) system, the atmosphere, etc. (or some combination thereof). An exhaust manifold that exists as an entity outside of the cylinder head occupies additional volume within the engine compartment and contributes additional weight to the overall system. It can also be cumbersome to navigate when repairs on the engine (or its components) are performed and space is limited. Attempts to address this problem of limited space include reducing the footprint of the exhaust manifold by incorporating it directly into the cylinder head as an integrated exhaust manifold (IEM). One such example of a single-port IEM is shown in WO 2013/045018.
However, the inventors herein have recognized potential issues with such systems. As one example, for a single-port IEM that is utilized in a three-cylinder engine, exhaust pulse interactions can occur when the runners join within the cylinder head leading to flow loss. The additional volume of the cylinder head required to join the runners can also reduce flow velocities. This can lead to a reduction in the energy supplied to a turbocharger and degradation of engine performance. While one approach may utilize a two-port external exhaust manifold, such as U.S. Patent No. 2014/0283799, this particular external solution leads to the issues described previously such as additional volume requirements and additional weight, as well as the increased cost of the manifold itself.
In one example, the issues described above may be addressed by an integrated exhaust manifold, comprising: first and second manifold exhaust ports; a first set of runners from a first cylinder; a second set of runners from a second cylinder; and a third set of runners from a third cylinder, where a first runner of the third set merges with the first set of runners at the first manifold exhaust port and a second runner of the third set merges with the second set of runners at the second manifold exhaust port. In this way, the integrated exhaust manifold may occupy a reduced volume, contribute less weight, and reduce exhaust communication between the first cylinder and second cylinder (which may be outer cylinders with the third cylinder positioned between the first and second cylinders) to reduce pulse interactions.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.